Double slit-valve doors for plasma processing

ABSTRACT

In a substrate vacuum processing chamber, a second inner slit passage door apparatus and method to supplement the normal slit valve and its door at the outside of the chamber. The inner slit passage door, blocks the slit passage at or adjacent the substrate processing location in a vacuum processing chamber to prevent process byproducts from depositing on the inner surfaces of the slit passage beyond the slit passage door and improves the uniformity of plasma in the processing chamber by eliminating a large cavity adjacent to the substrate processing location into which the plasma would otherwise expand. The inner slit passage door is configured and positioned in such a way as to avoid generating particles from the opening and closing motion of the second slit valve door, as it does not rub against any element of the chamber during its motion and the inner slit passage door is positioned with a predetermined gap from adjacent pieces and the door configuration includes beveled surfaces to further reduce the chance for particle generation, even when there is deposition of process byproducts on the door and its adjacent surfaces.

FIELD OF THE INVENTION

This invention relates to the construction of vacuum processing chambersused in processing of substrates for deposition and removal ofmaterials. A particular chamber configuration using a specialized lineris disclosed.

BACKGROUND OF THE INVENTION

In general, vacuum processing chambers for processing substrates includea substrate transfer opening, commonly known as a slit valve. A slitpassage (or passageway) associated with the slit valve is commonly usedto transfer substrates into and out of the processing chamber betweenprocessing cycles. Commonly a robot extends from a cluster tool througha slit valve opening through the slit valve passage to deliver or removea substrate to be processed to or from a processing location in thevacuum processing chamber. Once the substrate transfer at the substrateprocessing location is complete, the robot is retracted through the slitvalve opening and back into the cluster tool. The slit valve opening iscommonly sealed at an outside surface of the chamber body by a blockingplate which moves over the slit valve opening, in a coordinated motionwith the movement of the robot and substrate into and out of theprocessing chamber. Plasma is often used in a processing chamber toenhance the process being performed. In a typical arrangement of avacuum processing chamber, where a plasma is utilized to initiate orenhance process activity, the processing chamber and all internalservices exposed to the plasma and the chemical by products are affectedand can become coated with chemical byproducts of the process beingperformed.

Typically, the walls of the processing chamber are at least severalinches thick to provide a sturdy chamber wall for processing activity.Thus, the opening in the side of the processing chamber which allowssubstrates to be transferred into and out of the chamber, the slit valvepassage, presents a large tunnel-like opening which creates a geometricdiscontinuity at the inside surface of the processing chamber. Thepresence of a large cavity hole (the opening of the substrate transferpassage) adjacent to the space of the central processing location allowsthe plasma envelope which is present during plasma processing at thesubstrate processing location to expand into the cavity of the slitvalve passage. The expansion of the plasma envelope into the cavity ofthe slit valve passage creates a distortion in the portion of the plasmasituated adjacent to the cavity such that the plasma flux over thesubstrate in the area near the slit valve passage is affected, such thatthe deposition or etch taking place in that area is not uniform withother areas of the substrate where such distortion is not present.

Further, the internal surfaces of the slit valve passage, including theinside (process chamber facing side) of the slit valve door, are alsosubject to deposition and accumulation from the chemical process takingplace in the chamber. Deposition on the inside surfaces of the slitvalve passage and the slit valve door, require that any cleaning of thechamber (whether wet or dry) extend to include such surfaces. A thoroughcleaning of the slit valve door requires that it also be removed so thatthe full area of the door all the way to the sealing limit (vacuumcontainment limit to vacuum seal the opening) be cleaned. In mostinstances, door cleaning requires that the cluster tool be removed fromservice so that cleaning of one chamber does not cause potentialcontaminants from one chamber serviced by the cluster tool to be carriedover into a second chamber serviced by the same cluster tool.

The heavy duty sturdy construction of the processing chamber body andits liners finds no ready solution to the problem of the open cavityresulting from the slit valve passageway. Until now there has been nosolution to overcome these anomalies of prior art devices, in that allprior doors are constructed in a configuration that gives rise toparticles in the processing chamber.

SUMMARY OF THE INVENTION

A configuration according to the present invention overcomes thedrawbacks of the prior art by providing an internal slit passage doorwhich is cleverly constructed to improve the plasma uniformity over thesubstrate processing location and prevent deposition of chemicalbyproducts (such as polymers) in the slit valve passage. This second“internal” slit passage door is constructed as part of the chamber linerassembly so that when the chamber liner is replaced or a wet clean ofthe chamber liner is performed, the door is replaced and cleaned at thesame time.

One configuration according to the invention includes a chamber bodyenclosing a substrate processing location space. The chamber bodyincludes a slit passage extending from an outside surface of the body tothe substrate processing location space, where only one substrate isprocessed at a time within a vacuum containment limit the slit passagebeing sized to pass a substrate therethrough. An outer slit valve dooris positioned near the outside of the substrate transfer passage to sealthe outer end of the slit passage to the chamber. An inner slit passagedoor is positioned in an inner portion of the substrate transfer passageto block the substrate transfer slit passage at allocation near oradjacent to the substrate processing location.

Another configuration according to the invention can be defined withrespect to a liner surrounding a substrate processing location in thevacuum processing chamber where the liner includes a substrate transferopening therethrough. A liner door is selectively movable from an openposition where the substrate to be processed can be passed, to a closedposition where the liner door is located in close proximity to, but nottouching the surrounding liner around the substrate transfer openingsuch that the edges of the door overlap edges of the substrate transferopening. The overlap should preferably be approximately a half inch. Thegap between the door in its fully closed position and the surroundingliner (the surface adjacent an opening of the substrate transferpassage) is in the range of several tens of thousands of an inch(several times 0.254 mm) all around, but the door never touches theliner during operation. The door is curved to match the configuration ofa curved liner, for example, a circular liner configuration. Themovement of the door is vertical and selectively supported andcontrolled through a series of bellows which act as the vacuum limit ofthe processing chamber. The vertical motion limit of the door isprecisely set by a set of soft stops which prevent the door fromtouching the liner.

To reduce the chances for particle contamination, the bottom and topportions of the door are beveled to matched opposed beveled portions ofthe inner liner. With such a configuration the buildup of depositedmaterial on the inner surface of the door will not interfere withraising the door, as the clearance between the door and liner willincrease with each incremental distance that the door is moved from itsfully closed position towards an open position.

The invention further includes a method for reducing the buildup ofprocess byproducts on the surfaces of a substrate transfer passage andfor improving the uniformity of plasma in a vacuum processing chamberutilizing the steps of: providing a movable door to selectively blockthe substrate transfer passage at a location adjacent to the substrateprocessing location in the vacuum processing chamber, and moving themovable door out of the substrate transfer passage when a substrate isbeing transferred to or from the substrate processing location. Anothermethod according to the invention provides for operating a plasmachamber having a wafer transfer passageway between a substrateprocessing location and an outside surface of said chamber, includingthe steps of: (1) when plasma processing substrates: (1a) positioning awafer transfer passageway outer door to vacuum seal the transferpassageway; and (1b) positioning a wafer transfer passageway inner doorto isolate the transfer passageway between the inner door and the outerdoor from exposure to plasma; and (2) when transferring substratesthrough the wafer transfer passageway; (2a) positioning the wafertransfer passageway outer door and the wafer transfer passageway innerdoor to open the passageway to transfer substrates therethrough. Thedoor and door support structure may be movable between a door openposition and a door closed position without rubbing contact between anytwo items within the vacuum limits of the processing chamber.

The door is opened simultaneously with the external slit valve door topermit passage of a substrate into and out of the chamber (for example,by a robot blade). The support for the door prevents lateral movement ofthe door and assists in positioning it precisely in its down positionagainst a hard stop.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a processing chamber according to theinvention showing the outside of the chamber and a slit valve openingthrough which a substrate for processing can pass;

FIG. 2 is a partially exploded perspective view of the chamber top ofFIG. 1, the inner slit valve door and its actuator are shown separatedfrom the top flange of the processing chamber;

FIGS. 3A and 3B are exploded perspective views of the pieces of theinner slit passage door actuator and slit valve door according to theinvention;

FIG. 4 is a top view of the slit passage door and actuator mechanismaccording to the invention;

FIG. 5 is a cross-sectional side view of a configuration of a vacuumprocessing chamber according to the invention showing the use of anexternal slit valve door and internal slit passage door in relationshipto the substrate processing location of the processing chamber;

FIG. 6 is a cross-sectional view of the actuator mechanism for theinternal slit passage door according to the invention with the door inan up position;

FIG. 7 is a cross-sectional view of the actuator mechanism as shown inFIG. 6 with the slit passage door according to the invention in a lowerclosed position;

FIGS. 8, 9 and 10 are progressive assembly steps for moving the slitpassage door into position and securing it to its actuator showing theinstallation steps and the clearances between the inner slit valve dooraccording to the invention and a liner configured to receive the innerslit valve for the door;

FIG. 11 is a cross-sectional view of a slit passage door according tothe invention showing the location and configuration of lift rods whichconnect the actuator above;

FIGS. 12 and 13 show respectively the connections between the slitpassage door and the lift rods, FIG. 12 showing a fixed connection whileFIG. 13 shows a floating connection; and

FIG. 14 shows a top view of the slit valve door showing the slottedopening for the floating lift rod of the door.

DETAILED DESCRIPTION

FIG. 1 shows a perspective view of a typical semiconductor waferprocessing chamber 20. A frame 22 supports a chamber body 24. Thechamber body 24 at its front side has a slit valve passage 28 with anouter slit valve door (that cannot be seen in FIG. 1) to seal thechamber and a chamber top assembly 26. Adjacent to the chamber topassembly 26 is an inner slit passage door actuator assembly 30 shownwith its cover removed. Note that the inner slit passage door actuatorassembly 30 is on the same side of the chamber body 24 as the slit valvepassage 28 and the outer slit valve door (which cannot be seen) throughwhich wafers are passed into and out of the chamber 20.

FIG. 2 is a partially exploded perspective view of the chamber liner andtop assembly 40 including the inner slit passage door actuator assembly30. A chamber top plate (or flange) 42 at its center supports a topplate electrode cover 44 and on the side adjacent the slit valve passagesupports the inner slit passage door actuator assembly 30 which islocated by dowel holes 46, 48. A pair of door lift rods, the left rodbeing the fixed lift rod 200 and the right rod being the floating liftrod 210 pass through their respective holes in the chamber top plate 42to fit into holes in the top of inner slit passage door 60. As can beseen in FIG. 2 the inner slit passage door 60 is curved to match theradius of the chamber liner assembly 50. The inner slit passage door 60is attached to the lift rods 200, 210 by a rod retaining screw 72 and ashoulder screw 82, respectively. The inner slit passage door 60 fits ina slit door recess 54 in the chamber liner assembly 50 so that when theinner slit passage door 60 is in its down position, it covers andoverlaps the slit opening 52 in the liner assembly 50.

FIGS. 3A and 3B show an exploded perspective view of the parts of theinner slit passage door 60 and vertical actuator assembly 30. A top viewof the assembled actuator assembly 30 is shown in FIG. 4, while adetailed cross-sectional view of the actuator assembly is shown in FIG.6. In the description that follows, all of these Figures should bereferenced to thoroughly understand how the door support rods 200, 210support and precisely position the inner slit passage door 60 as itmoves up and down.

An actuator base 100 is supported on the chamber top plate 42 (forexample, as shown in FIG. 2). The base 100 includes a large dowel pin186 and a small dowel pin 188 (FIG. 6) which fit into large and smalldowel pin holes 46, 48, respectively, in the chamber top plate 42. Thedowel pins fit tightly in these holes and their two different sizesprevent an incorrect installation. The lower surface of the actuatorbase 100 includes a set of two O-ring grooves each having an O-ring seal(e.g., 132, 134) surrounding the lift rods 200, 210 passing throughopenings in the bottom of the actuator based 100. A set of two bellowsmounting tubes 102, 104 which are integral with the base 100 extendvertically from the bottom portion of the base to provide an enclosurefor a set of rod lifting bellows assemblies 120, 140. Each rod liftingbellows assembly (e.g., 120, 140) includes an intricately assembled setof pieces which guide each of the lift rods as they move up and down andrestrict their sideways motion while maintaining a vacuum seal acrossthe bellows without any rubbing parts. Each rod lifting bellows assembly(e.g., 120, 140) includes a bellows central rod 128 which extends from atop of the assembly all the way through to its bottom. At the bottom ofthe assembly, a lower rod receiving portion 121 includes a threaded holefor receiving an upper end (e.g., 202) of one of the door lift rods(e.g., 200, 210). The lower portion 121 of the central rod 128 extendsdown below a lower bellows flange 122 that extends laterally outwardfrom the central rod 128. At the perimeter of the lower bellows flange122, a cylindrical set of corrugations form a cylindrical bellowsattached to the perimeter of the flange 121. The upper end of thecylindrical bellows 123 is welded to an upper bellows flange 124. Theperimeter of the upper bellows flange 124 extends out over the end ofthe top of the bellows mounting tube 102 and includes a downwardlyfacing inner recess to fit over a raised inner ledge/seal flange 114(FIG. 3A) of the bellows mounting tube 102, against which a sealingO-ring 106 is positioned. The bellows flange 124 at its center includesan upwardly extending guide bearing support tube 126. A tightly fittinglower rod guide bearing 125 is supported at a lower end of the guidebearing support tube 126, while an upper bellows rod guide bearing 127is supported at an upper portion of the tube. A travel stop tubeassembly 150 includes a lower flange 152 and a tube portion 154. Thelower flange 152 sits on and seats against the upper bellows flange 124and the upper surface of the bellows mounting tube 102. The travel stoptube assembly 150 surrounds the guide bearing support tube 126. The tubeportion 154 of the travel stop assembly 150 extends to a tube end 158which has an O-ring groove 156. An O-ring 168 is placed in the O-ringgroove 156 and acts as a bumper to dampen the shock of stopping when theactuator assembly moves down and contacts the end 158 of the travel stoptube assembly 150. The travel stop tube assembly 150 acts as a hard stopto prevent further downward motion of the inner slit passage door 60.

The upper end of the bellows central rod (e.g., 128) is connected to afloating joint 174 which restricts vertical motion (Z-axis) but allowsX-Y axis motion and also angular (spherical-type tilting) between thetwo halves of the joint. This floating joint allows for minormisalignments without creating any binding forces that might prevent aneasily operable vertical stroke.

At the bottom end of the bellows central rod 128 a top end of the fixedlift rod 200 includes a threaded portion which is threaded into the holein the lower portion of the bellows central rod 121 and also includes aflange which acts as a stop to tightly control the overall verticaldimension of the fixed lift rod 200 with respect to the bellows centralrod 128. The flange contributes to achieving the tight tolerance invertical positioning (spacing) that is very important in thisconfiguration so that a specified gap between parts is maintained, buttouching of such parts does not occur. In the configuration as shown,the lower portions of the two central rods shown, as will be discussedin detail later, are fixed to the inner slit passage door 60 by thefixed screw 72 and the shoulder screw 82.

Compared to the left side rod lifting bellows assembly 120 describedabove, the right side rod lifting bellows assembly 140 containsidentical components and is sealed to a right side seal flange 116 by anO-ring 108 (FIG. 3A). The top end of the right side rod lifting bellowsassembly 140 is also enclosed by a travel stop tube assembly 160 whichcontains an O-ring bumper 170 at its top surface and the central bellowsrod of the right side (floating side) can connect to a right-sidefloating joint 176.

The two floating joints 174, 176 are connected at their top ends to arod lift cross member 180 which is rigidly fixed to the pneumaticactuator rod 112 of a pneumatic actuator cylinder contained in apneumatic actuator base 110 by a pneumatic actuator connection bolt 182.The limit of the upward vertical motion is set by the limit on thepneumatic actuator 110 and the motion limits of the pneumatic rod 112.High pressure air (for example, 60 to 80 psi (0.414 to 0.551 MPa)) iscommonly used to move the actuator up or down as required. With suchhigh pressure, the force will be fast acting and the rigidity of thepneumatic actuator rod 112 along with its tight clamping to the rod liftcross member 180 along with the use of floating joints 174 and 176prevents there from being any binding as a result of the door lift rodsor the bellows central rods being out of alignment with the pneumaticactuator 112.

FIG. 6 pictures the fully up position of the inner slit passage door 60positioned above the top edge of the slit opening 52 in the linerassembly 50.

FIG. 7 shows the same elements of the actuator assembly as in FIG. 6 butthe inner slit passage door 60 is shown in its lowered position and thepositions of all actuator elements correspond to their positions whenthe rod lift cross member 180 contacts the tops of each of the traveltube assemblies 150, 160 to prevent the door 60 from descending further.In this configuration is can be seen that the inner slit passage door 60overlaps the edges of the slit opening in liner 52 by an equal amountall around of approximately one half inch.

The vacuum limits (vacuum containment limits) of the processing chamberextend into the actuator assembly. The O-rings 132, 134 which the sealthe bottom of the actuator base 100 against the top of the chambered topplate 42 provide one seal. A second seal is provided by the O-rings 106,108 configured between the upper bellows flanges (e.g., 124) and the topend flange/lip 114 of the bellows mounting tube 102 (FIG. 3A). Thecylindrical bellows corrugation (e.g., 123) which is welded between thelower bellows flange 122 and the upper bellows flange 124 completes thesealing/separation between the atmosphere and vacuum while stillallowing the actual vertical movement without their being any particlesgenerated as a result of rubbing two pieces within the vacuum chamber.The guiding of the central rod (e.g., 128) by the linear guide bearings(e.g., 125, 127) in the bellows assembly is located in atmosphere andparticles thus generated have no effect on processing within the vacuumchamber.

An element of the proper location of the inner slit passage door 60 andits movement are the tight dimensional tolerances specified for the base100. The use of an integral large base which is dimensioned andtoleranced very tightly (several thousands of an inch in most instances)assures that appropriate dimensional relationships between the innerslit passage door 60 and the adjacent liner assembly 50 are maintained.

FIG. 4, a top view, shows the curved configuration of the inner slitpassage door 60 with respect to the two rod lifting axes of the bellowsassemblies 120, 140 as positioned on the base 100 of the actuatorassembly 30.

FIG. 5 shows an elevational cross sectional view of a processing chamberwith a substrate processing location 220 (i.e., a substrate on asubstrate support at the processing location within a processingchamber) being located opposite a substrate transfer passage 222 suchthat a slit valve door 224 at the outside of the passage and the innerslit passage door 60 obstruct the passage of a substrate from theoutside of the chamber to the substrate processing location 220. Theslit passage actuator assembly 30 is located above the inner slitpassage door 60 (some internal elements of the actuator assembly are notshown in this view).

FIGS. 8, 9, and 10 show the progressive installation sequence of thedoor 60 using cross sectional views along the vertical hole passagesthrough the door which mate with the door lift rods 200, 210. In FIG. 8,the lift rod 210 is shown in a retracted (up) position with respect tothe chamber top plate 42.

The inner slit passage door 60 has a lower counterbore bolt hole 61, anarrow pass through hole 63 and a top rod receiving hole 65. Duringassembly, the inner slit passage door 60 is moved into position underthe door lift rods in the liner assembly 50.

The construction of the inner slit passage door 60 is such that thethickness of the door, (more particularly the position of its frontface) changes from top to bottom such that there is a lower beveled face62 at the bottom portion of the slit passage door 60, there is uniformthickness face area 64 (which here is shown straight (i.e., vertical),but in an alternate configuration may be may be slightly angled orbeveled) and an upper beveled face 66 where the thickness of the doorincreases towards the top. The beveled faces match lower 84 and upper 86beveled faces on the liner inner wall portions 94, 96 such that when inposition as shown in FIG. 10, the gaps (e.g., 88, 90) between the frontfaces (62, 66) of the inner slit passage door 60 and the facing linerupper and lower surfaces (84, 86) are approximately several tens ofthousandths of an inch (several times 0.254 mm).

The gap dimensions (e.g., 88, 90) are maintained to prevent any plasma(and processing byproducts such as polymers) from moving into thesubstrate transfer passage 222 as it does in the prior art. Further thisgap is large enough so that the risk of the door touching (rubbingagainst) the liner during operation is minimized so that particles arenot created, but the gap is tight enough so that plasma is choked andchemical byproducts (byproducts of the processing which tend to coat thesurface of the processing chamber facing it) cannot pass through.Further build up of films which do deposit on the surface of the innerpassage door 60 have a minimal effect in that the bevels on the face ofthe liner and the matching top and bottom and partial beveled surfacesbevel in the slit valve door mean that the closest approach between theliner and the door is when it is in a fully closed position. As soon asthere is any motion to the open position, the gap, for example as shownin FIGS. 9 and 10, gap dimension 90 in FIG. 10 increases tremendously tobecome gap dimension 92 in FIG. 9.

FIG. 3B shows in a perspective view the beveled orientations of theupper and lower chamber liner portions 94, 96 with their respect tofaces 84, 86. The end 56 of the slit opening 52 is positioned short ofthe edge of the recess 54 in the liner assembly 50 so that once theinner slit passage door 60 is put into position the end of the dooroverlaps the end 56 of the slit 52 by a distance approximately equal tothe overlap of the top and bottom edges as discussed above.

The progression of the assembly is shown in FIGS. 8, 9, 10. Theretracted door lift rods receive the inner slit passage door andretaining screws are inserted and tightened so that the door can then beactuated. A frontal view of the door with the lift rods 200, 210 asshown in FIG. 11 as might be expected, the door being made of aluminumwill tend to expand and contract with variations in temperature, as willdoors made of any material that has a coefficient of thermal expansionthat tends to create binding on lift member depending on the dimensionalrelationships established and the range of temperatures to beaccommodated.

The requirement of positional accuracy and the freedom for thermalexpansion is accommodated by making one door support rod, the left rod200 here, a fixed rod such that the end of the rod 200, for example, asshown in FIG. 12 is tightly clamped to the fixed hole configuration inthe slit valve door. The machine screw 72 engaging the end of the rodtightly clamps the end of the rod 200 to the shoulders of the narrowpass through hole 63 in the inner slit passage door 60. This tightclamping provides a good electrical path to ground from the door, sothat the possibility of arcing is reduced or eliminated, and furthersets a horizontal and vertical position of one end of the door. Thisclamping acts as an anchor (or pivot) around which the other floatingend of the door and its support can move.

FIG. 13 shows the right-hand rod, floating rod 210. Its rod receivinghole 68 is elongated in a sideways direction (e.g., FIG. 14) to allowfor some expansion and contraction while the lower end of the rod isvertically fixed by a shoulder bolt 82 which clamps tightly against thebottom end of the floating rod 210. The narrowness of the slot 68prevents sideways (radial) motion. Note that there is a gap 74 betweenthe end of the rod and the inwardly protruding flanges (shoulders) ofthe rod through hole 63. The floating rod can thereby tilt, but isvertically fixed by the end flange (head) of the shoulder bolt 82 toallow free contraction and expansion of the slit passage door 60 astemperature variations take place about the fixed central axis of thefixed lift rod 200. Since the temperature variation is onlyapproximately 100 to 150 degrees from ambient and the distance betweenthe two lift rod holes is approximately six inches, the expansion willbe quite manageable with this configuration.

A configuration according to the invention as has been described abovetypically includes an outer (chamber sealing) slit valve assembly. Thepresent invention provides an inner slit passage door to block thedeposition of polymers and other byproducts of the process in thechamber from depositing on the wall of the processing chamber. In thisconfiguration the inside of the outer slit valve door does not have tobe cleaned during a normal cleaning of the processing chamber.Therefore, the seal (which isolates each process chamber processing onewater at a time from the transfer chamber) between a transfer chamber ofa cluster tool is not affected if one of the chambers needs to becleaned, whereas in the past, chamber cleaning always meant that thecluster tool and its transfer chamber was disrupted. Another benefit ofa configuration using an inner slit passage door as described herein isto improve the uniformity of the distance between the edge of thesubstrate being processed at the substrate processing location in thechamber and the surrounding liner which defines the limits of the plasmaenvelope over the substrate all this inside the processing chamber whichoutside the lines also acts to confine the substrate processingenvelope. In the conventional configuration there was a large hole inthe chamber liner which allowed plasma to expand into it. The expansionof plasma created a distortion on the plasma flux over the substratebeing processed and variations in substrate processing from the sideclosest to the substrate transfer passage to the opposite side werenoted. In a configuration according to the invention, the discontinuityin the plasma flux due to the slit transfer passage has been eliminated,by the substitution of a door at the same electrical potential as theliner, to create a nearly uniform distance between the edge of thesubstrate being processed and the liner lining the wall of theprocessing chamber adjacent to the substrate. The configurationaccomplishes this without substantially increasing the risk thatparticles will be generated in the chamber either by the movement of adry door, or by movement of a door whose exposed surfaces have beencoated with process byproducts. The bellows assembly seal provides drysealing, without introduction of particles, while the cleverly curvedand/or beveled surfaces of the door and the liners surfaces that itfaces reduce the risk of polymer flake off, and peel off duringoperation. The door can be easily removed and cleaned as a unit with theliner assembly thereby simplifying the maintenance steps need to achievea clean chamber, to return the chamber to production as soon aspossible.

While the invention has been described in regards to specificembodiments, those skilled in the artwork recognize that changes can bemade in form and detail without departing from the spirit and scope ofthe invention.

We claim:
 1. A plasma processing chamber for confining a substrateprocessing plasma envelope, said chamber comprising: a substrate supportto position a substrate at a substrate processing location to be exposedto said substrate processing plasma envelope; a substrate transferpassageway extending through a wall of said chamber from an outsidesurface of said chamber to a position adjacent said substrate support;an outer slit valve door at an outer position of said substrate transferpassageway to selectively vacuum-seal said transfer passageway andchamber during plasma processing; and an inner slit passage door at aninner position of said passageway to exclude said passageway fromexposure to said plasma envelope during plasma processing.
 2. The plasmaprocessing chamber as in claim 1, wherein said inner slit passage door,when positioned to block said substrate transfer passageway, extendsbeyond the edges of said passageway by an overlap distance.
 3. Theplasma processing chamber as in claim 2, wherein said overlap distanceis at least ¼ inch (6.35 mm).
 4. The plasma processing chamber as inclaim 2, wherein said overlap distance is approximately ½ inch (12.7mm).
 5. The plasma processing chamber as in claim 1, wherein said innerslit passage door is curved to match the configuration of a chamberliner.
 6. The plasma processing chamber as in claim 2, wherein saidinner slit passage door is curved to match the configuration of achamber liner.
 7. The plasma processing chamber as in claim 3, whereinsaid inner slit passage door is curved to match the configuration of achamber liner.
 8. The plasma processing chamber as in claim 1, wherein amovement of said inner slit passage door is in a vertical direction andis selectively controlled through movement of a bellows assembly throughwhich a support for said inner slit passage door is provided.
 9. Theplasma processing chamber as in claim 8, wherein said inner slit passagedoor is supported by two support rods.
 10. The plasma processing chamberas in claim 9, where a first of said two support rods is fixed to saidinner slit passage door through a tightly clamped connection, while asecond of said two support rods is connected to said inner slit passagedoor through a floating connection which maintains said inner slit valvedoor's orientation in a vertical direction and in a directionapproximately perpendicular to a long axis of said door, and is allowedto move in a direction approximately along said long axis of said door.11. The plasma processing chamber as in claim 1, wherein said inner slitpassage door in a closed position is located with a gap of several tenthousandths of an inch from a surface adjacent an opening of saidsubstrate transfer passageway.
 12. The plasma processing chamber as inclaim 8, wherein the limit of the movement of said inner slit passagedoor in a vertical direction is precisely set by at least one soft stop.13. The plasma processing chamber as in claim 2, wherein top and bottomportions of said inner slit passage door are beveled to match opposedportions of a portion of a surface of the chamber that they face. 14.The plasma processing chamber as in claim 13, wherein a center portionof said inner slit passage door is beveled to match an angled surface ofa portion of a surface of said chamber through which said substratetransfer passageway extends.
 15. The plasma processing chamber as inclaim 1, wherein said inner slit passage door and said outer slit valvedoor open simultaneously to allow passage of a substrate in to and outof the chamber.
 16. A plasma processing chamber for confining asubstrate plasma envelope, as in claim 1, wherein said outer slit valvedoor is disposed between the plasma processing location and a transferchamber located outside said processing chamber at an end of saidsubstrate transfer passageway.